Unsubscribing

How can you help someone unsubscribe if they forgot their password?
I work at a country club and a member subscribed to the blog. They want to unsubscribe and they want me to do it for them. They can't remember the email address they used or the password. I've tried to walk them through the steps and they can't figure it out. Is there any other way to unsubscribe them so they stop getting emails when there is a new blog post? He is now posting comments to stop sending which of course don't work. I know he is getting frustrated. Any help you can offer would be much appreciated. Thanks!
Blog url: http://glenmoorcc.wordpress.com/